Common Name: By-the-wind-sailor
Distribution: Common throughout the Solitary Islands Marine Park. Found in all the worlds warm and temperate oceans.
Ecological Notes: Floats on the ocean surface, feeding on plankton which it catches with short tentacles.
Additional Notes: Each “individual animal” is actually a hydroid colony, with many polyps that feed on plankton. These polyps are connected by a canal system that enables the colony to share whatever food is ingested by individual polyps. Drifting at mercy of the winds, they may sometimes be stranded on beaches in large numbers. The small rigid sail aligns with the wind and acts as an aerofoil, subsequently causing the animal to move across the water surface at a slight angle to the wind direction. Known predators include the Common Violet Snail, Janthina janthina. Grows to about 7cm maximum size.
References: Bennett, Isobel, Australian Seashores, Angus and Robertson Publishers. 1987. p 167.